Hello,
I can take a look at your Excel COM Add-in to see if I can figure out why it's not working in Office 365 Excel and then fix it. If you like, we can do this project as a fixed price project. You don't have to pay unless the COM add-in is fixed to work in Office 365 Excel. I will provide you with the fixed price estimate after I test and examine the Add-in.
If you like, we can chat to see if I can help.
Thanks